Container having improved bellows closure and blank for making same

ABSTRACT

A corrugated fiberboard container having an improved bellows closure biased to remain in closed condition, once folded, and thereby eliminate the necessity of gluing closure flaps prior to filling. Illustrated is a container having a bellows bottom closure made up of four interconnected panels of equal length wherein diagonal score lines which do not meet provide trapezoidal closure flaps. The length of the closure panels provides an overlapping of the longer closure flaps in the closed condition with the edge of one flap nesting within the edge of the other. Slits are provided in the glue flap in the closure region which permit the glue flap to be hinged to the longer side wall and adhered to the shorter end wall thereby leaving the side wall unobstructed.

United States Patent Ellison 3,750,932 Aug. 7, 1973 [75] Inventor:Donald E. Ellison, Clayton, Ind.

[73] Assignee: Inland Container Corporation,

Indianapolis, Ind.

[22] Filed: July 28, 1971 [21] Appl. No.: 166,921

[52] US. Cl. 229/37 R, 229/D1G. 2, 229/DIG. 4 [51] Int. Cl B65d 5/02[58] Field of Search 2,29/17 R, 17 G, 37 R, 229/DIG. 2, DIG. 4

[56] References Cited UNITED STATES PATENTS 3,529,763 9/1970 229/37 R2,470,789 S/l949 229/17 R 1,624,439 4/1927 229/37 R 3,343,750 9/1967229/37 R R25,021 8/1961 229/17 G 2,195,922 4/1940 Gibson et al......229/17 R 3,341,104 9/1967 Loheed et al. 229/17 R 1,994,923 3/1935 Ross229/17 R FOREIGN PATENTS OR APPLICATIONS 471,003 5/1969 Switzerland229/DIG. 4

Primary ExaminerI-lerbert F. Ross Assistant Examiner-Stephen MarcusAttorney-Fitch, Even, Tabin & Luedeka [57] ABSTRACT A corrugatedfiberboard container having an improved bellows closure biased to remainin closed condition, once folded, and thereby eliminate the necessity ofgluing closure flaps prior to filling. Illustrated is a container havinga bellows bottom closure made up of four interconnected panels of equallength wherein diagonal score lines which do not meet providetrapezoidal closure flaps. The length of the closure panels provides anoverlapping of the longer closure flaps in the closed condition with theedge of one flap nesting within the edge of the other. Slits areprovided in the glue flap in the closure region which permit the glueflap to be hinged to the longer side wall and adhered to the shorter endwall thereby leaving the side wall unobstructed.

15 Claims, 6 Drawing Figures Pmmwwv 1w 3.750.932

SNEH 1 0f 2 INVENTO DONALD E. E SON m, M, Tabm, $5M

ATTYS.

PAIENIEDAUB SHEET 2 BF 2 FIGS INVENTOR DONALD E. ELLISON PM 6 91, TIM,

ATTYS.

CONTAINER HAVING IMPROVED BELLOWS CLOSURE AND BLANK FOR MAKING SAME Thepresent invention relates to containers adapted to be folded from ablank and, more particularly, to a container made of corrugatedfiberboard having a bellows type closure and to a blank from which sucha container may be folded.

Bellows-type closures have long been known and found to be usable fortubular containers including containers made of corrugated fiberboardand the like. In recent years, it has become desirable to employ largecorrugated fiberboard containers for the shipment of bulk materials, forexample, particulate chemical resins and other flowable materials, suchas synthetic rubber and the like. Such bulk containers are fabricated ofstrong materials, such as double wall and sometimes even triple wallcorrugated board, and they are often reinforced in various ways toeffectively withstand the internal loads which may reach as high as twotones. The strength provided by the bellows-type closure, particularlyfor the bottoms of boxes, has been found to have application in thefield of bulk containers.

However, the substantial thickness of the material from which the blanksfor such bulk containers are fabricated gives rise to various problemswhich are simply not encountered in ordinary bellows closures employedon simple paperboard material, such as milk cartons presently used inthe United States. For example, the strength and resiliency of doublewall corrugated fiberboard creates an inherent biasing of the bellowsclosure to the open position; a problem in handling empty containers.Moreover, when a glue flap is provided to establish a manufacturersjoint at one of the corners of the bulk container having a bellows-typeclosure, that flap has been hinged to one of the shorter end panels sothat it is laminated to a side panel from which there depends a closureflap that is not scored to form triangular fold-back panels. Thisarrangement is illustrated in U.S. Pat. No. 3,523,635 and has limitedthe configuration of. such containers. Accordingly, improvedbellows-type closures, particularly suited for use in bulk containers ofcorrugated fiberboard, are desired.

An object of the present invention is to provide a container having animproved bellows-type closure.

Another object of the invention is to provide a container having abellows closure which when folded into a closed position is biased toremain closed.

A further object is to provide a blank for a tubular container having abellows-type closure which is adapted to facilitate the folding of sucha closure even though the blank is fabricated from strong, stifffiberboard.

Still another object of the invention is to provide a container having abellows-type bottom closure which when set up will rest flat upon asupporting surface even though empty,\vithout gluing the closure panelsto one another.

These and other objects of the invention shouldbe-v come clear upon areading of the following detailed description, while making reference tothe accompanying drawings, wherein:

FIG. 1 is a perspective view of a container having a bellows-type bottomclosure embodying various features of the present invention;

FIG. 2 is a plan view of the blank from which the container shown inFIG. 1 is formed;

FIG. 3 is a perspective view of the container illustrated in FIG. 1shown in inverted position with the bottom closure in a partially closedcondition;

FIG. 4 is a perspective view similar to FIG. 3 illustrating thecontainer with the bottom closure in a fully closed position;

FIG. 5 is an enlarged, fragmentary sectional view taken along the line5-5 of FIG. 3; and

FIG. 6 is an enlarged fragmentary sectional view taken along line 6--6of FIG. 4.

Illustrated in the drawings are a container 11 and a blank 13 from whichthe container 11 is formed. The illustrated container 11 is designed]particularly for the transport of bulk materials, and the blank 13 isaccordingly formed from double wall corrugated fiberboard. The container11 has four upstanding vertical walls which are referred to in thefollowing description as side walls 15a and 15b and end walls 16a and16b; however, it should be understood that the terminology is employedfor ease of reference only and, insofar as the concept of the inventionis concerned, the terms should be considered interchangeable. The blankmay also be part of a total container containing a laminated 7 liner orliners, or it may be part of a multicell container containing one ormore of such blanks. In the blank 13, the end walls and the side wallsare defined by four longitudinally extending, parallel score lines 17a,17b, 17c and 17d, by a transverse upper score line 19a and by atransverse lower score line 19b. The blank is preferably made fromcorrugated fiberboard having flutes which run parallel to the lines 17and extends longitudinally both above and below the transverse scorelines 19. Thefour parallel score lines 17 extend to the lower edge ofthe blank, thereby defining a first pair of closure flaps 23a and 23bwhich are hinged to the side walls 15 and a second pair of closure flaps25a and 251) which are hinged to the end walls 16.

As can be seen from FIG. 2, the lower and upper edges of the blank 13are straight. At its upper end,the blank 13 is slotted at what wouldotherwise be extensions of the four parallel score lines l7.above thetransverse score line. These slots create four separate un connectedupper flaps 27a, 27b, 27c and 27d. Although the container 11 isillustrated as having such separate flaps 27 of the type sometimesemployed as a part of an interlocking cap arrangement, it should beunderstood that the illustrated upper portion of the container 11 formsno part of the present invention. Accordingly, the upper portion of thecontainer 11 could be fabricated with any type of an upper closure, orno closure at all with the blank 13 simply ending at what is illustratedas the upper transverse score line 19a. Likewise, it should beunderstood that the improved bellows clo sure, as hereinafter discussedin detail, which is provided by the interconnected closure flaps23a,23b, 25a and 25b could equally well be providedat both the top andbottom of a container, or it might conceivably be only provided at thetop of the container while a standard bottom construction i s used. V,

In the illustrated embodiment, a glue flap 29 for creating amanufacturers joint at one corner of the container 11 is hinged to theside wall 15a along the vertical score line 17a. The glue flap 29extends from the upper transverse score line 19a to the lower edge ofthe blank and is designed to be attached by adhesive or by stitching tothe outersurface of the end wall panel 16b and thereby form the flatblank 13 into a tube. Other types of manufacturers joints may also beused in different embodiments of containers wherein the improved closureis included. For example, in a multicell container a tapped, butt jointin one of the side walls might be employed.

As best seen in FIG. 2, the first pair of panels 23a and 23b areprovided with pairs of converging score lines 31a and 31b, respectively,which extend from the intersections of the score lines 17 with thetransverse score line 19b and which along with the lower transversescore line 19b and the lower edge of the blank define first closureflaps 33a and 33b that are trapezoidal in shape. The four parallel scorelines 17 and the upper and lower transverse score lines 19 are allformed upon what eventually becomes the inner surface of the container11, whereas the score lines 31 are preferably formed on the outersurface of the blank for a purpose to be explained hereinafter.

In each of the second pair of closure panels 250 and 25b attached to theend panels 16a and 16b are provided another pair of converging diagonalscore lines 35a and 35b, respectively, which extend from theintersections of the score lines 17 with the transverse score line 19band form in those panels two smaller trapezoidal flaps 37a and37b,'which are nearly triangularin shape as a result of the very shortlower side. The score lines 31 and 35 alternately define pairs oftriangular fold-back panels 39a and 39b located mainly in the endclosure panels 25 but extending slightly past the respective parallelvertical score lines, as seen in FIG. 2. These triangular fold-backpanels include the angle A which should be slightly less than the angleD (between the transverse score line 19 and the diagonal lines 35) inorder to obtain the over-center closing action described hereinafter.The angle A is also less than 45, and the angle D is usually between 46and 54.

As illustrated in FIG. 3, the folding of the bottom bellows closure iscarried out by first bending the larger closure flaps 33a and 33b,hinged to the side panels of the container, inward after the blank 13has been set up from its knockdown shipping condition to an open tube.Because the score lines 31 and 35 are preferably printed on the exteriorsurface of the blank, the panels 37a and 37b are first pushed inward toinitially break the score lines 35a and 35b. Then, the side closure flap33a is folded first, followed by the other flap 33b, causing the slightoutward displacement of the end trapezoidal flaps 37a and 37b as shownin FIG. 3. As can be seen, the length of the flaps 33 is sufficient sothat they overlap by at least a predetermined distance.

As shown in FIG. 5, in this intermediate position, both of the flaps 33are oriented at an angle slightly above the horizontal plane defined bythe hinge line 19b, i.e., slightly exterior of the cavity of thecontainer 11. The folding of the closure is completed by grasping thegenerally triangular end closure flaps 37 and swinging them and theattached fold-back panels 39 inwardly until the flaps 37 are alignedsubstantially in the horizontal plane of the hinge line 19b.

At the end of this swinging movement, the bellows closure actually snapsinto closed position as a result of the movement of the side flaps overcenter. This over center action is best seen by comparing FIGS. and 6which show sectional views of the container closure in the intermediateposition and in the closed position. The over center action results fromthe location of the score lines 31 and 35 so that, as seen in FIG. 5,the

angle A between score lines 35a and 31b is less than the angle D betweenscore lines 35a and 19b.

There is some latitude in the angular orientation of these score lines31a and 31b depending upon the relative widths of the side panels andthe end panels and upon the strength and thickness of the material fromwhich the blank is fabricated. In order for the flap 23b to nest insidethe flap 23a (FIG. 3), the angle B at which the score lines 31b areoriented relative to the transverse line 19b should be less than theangle C at which the lines 31a are oriented. For a container of thistype to have a satisfactory over-center action in the closing of thebellows-type closure, the angle A between the score lines 35 and thescore lines 31b on the panel 23b to be folded inward second, andthusnest within the other, should be between about 2 and about 9 lessthan angle D formed by score lines 35 and hinge line 19. Variablesinclude size, amount of overlap if used, and rigidity of containermaterial. Thus, the precise angular orientation of the score lines 35 isdependent partially upon the location of the line 31; however, the angleD is greater than 45 for meeting or overlap flaps. In general, theangles B and C will be between about 82 and 89 degrees. However, so faras the angle C is concerned, it can approach 90, and in some containersit is possible toeliminate the lines 31a and only employ six diagonalscore lines, i.e., 3lb,.35a and 35b. Thus, because it might beeliminated, the angle between the diagonal lines 31a and 35a is labeledA. Also, slots or slit cuts, particularly on the panel 23a to be foldedfirst, can be used to further provide for ease of folding whileretaining all advantages of this improved bellows closure.

As previously indicated, the longitudinal length of the side closurepanels 23 should be such that there is a sufficient overlap of the sideflaps 33 in the closed position so that the outer edges 43 of theseflaps do not interengage. The closed position is illustrated in FIG. 6,and it can be seen that the necessary amount of overlap will bedependent upon the width of the end panels 16 and upon the angle whichthe flaps are disposed interiorly of the end plane of the container 11in this closed position, which angles are indicated by the referenceletter B in FIG. 6. As a general rule, it is preferred that thelongitudinal length of the closure panels 23 be at least equal to aboutpercent of the width of the end panel 15; however, dependent upon othervariables in the construction, there may be sufficient overlapping whenthe length is only 52 percent of the end panel width.

As shown in FIG. 2, all of the bottom closure flaps 23, 25 are of thesame length which permits economical fabrication because die cutting isrendered unnecessary. Although the length of the bottom flaps could beextended up to a point where interference between the flaps 37a and 37bwas encountered, such extension is not considered to achieve any usefulpurpose and is disadvantageous because it would increase the cost of thecorrugated board. Thus, it is unlikely that the length of the bottompanels would exceed about percent of the width of the side panels.

In the illustrated embodiment, .the container 11 is provided with amanufacturers joint at the corner which is formed by the glue flap 29,the interior surface of which is coated with adhesive and then laminatedto the outer surface of the end panel 16b and the end closure panel 25b.When the container blank 13 is made from a strong, thick material, suchas a doublewall corrugated fiberboard or a laminated construction, thetwo thicknesses which are created at the location where the glue flap islaminated have been found to exert a considerable restraint to bending.As can be seen in FIGS. 3 and 4, one bend of 90 is required and one bendof substantially 180 is required when the glue flap 29 is laminated toan end panel 16 to leave the side panels free from obstruction. It hasbeen found that by slitting glue flap 29, immediate relief from thisrestraint is provided.

As seen in FIG. 2, a horizontal slit 45 is provided in the glue flap 29located at the extension of the lower hinge line 1%. Moreover, a secondslit 47 is provided at an angle generally the same as the angle of thescore line 35b. The second slit facilitates the 180 bend at the point ofhinging to the fold-back flaps 39. As can be seen in FIG. 4, the slits45 and 47 define a small triangular panel 49 at the edge of the blank.If desired, this panel can be removed by extending both slits all theway to the intersection between the vertical score line 17a and thehinge line 19b. However removal of the small panel 49 is not required,and to facilitate fabrication it may be desirable to terminate the slits45, 47 short of the intersection.

In summary, the scored blank 13 is fabricated as shown in FIG. 2, withthe score lines 17 and 19 being located on what will be the interiorsurface of the container 11 and with the diagonal score lines 31 and 35printed on the exterior surface. Adhesive is applied to the glue flap29, and the end panel 16b and the side panel 15a are folded about theparallel score lines 17d and 17b, respectively. Compression is thenapplied to the blank to form the manufacturers joint. The container 11is shipped to the place of ultimateuse in this flat or knocked downcondition.

To set up the box for filling, the flattened, seamed blank is invertedand formed into a tubular shape by squeezing at the score lines 17b and17d. The score lines 35 are then broken by momentary inward applicationof pressure to the panels 25. The side closure flaps 33 are then foldedinward to the relatively stable position shown in FIG. 3. The endgenerally triangular closure flaps 37 are then swung about their hingelines inward until they are aligned substantially in the end plane ofthe container, defined by the peripheral hinge line 19b. In reachingthis position an over-center action occurs as the side closure flaps 23aand 23b snap interiorly into the location shown in FIG. 6. In thisposition, the closure is stable as a result of the over-center action.Accordingly, the container 11 can be turned right side up and will setflat upon a level surface, such as the floor. However, because of theweighjt of the filled bulk container, it is usually disposed upon apallet, such as that depicted in FIG. 1 to facilitate its handling bymechanical lift equipment.

As a result of the stable, over-center position, the empty container 11can be moved without gluing the bottom closure to the filling location.Once the container is filled with hundreds of pounds of contents, thebottom closure is of course compressed between the contents and theupper surface of the pallet 51, and it thereafter remains tightly closeduntil it is emptied or removed from the pallet. Accordingly, if it isthe intention to employ the container either with an associated pallet,or perhaps by disposing it inside ofa bottom cap, the bottom flaps ofthe bellows-type closure need not be glued to one another. Of course, ifdesired, total sealing of the bottom closure may be achieved by applyinga glue pattern to the triangular fold-back panels 39 and optionallyalong the lower exterior edgev of the underlying side closure flap 33b.The containerr 11 may advantageously be used without gluing the bottomclosure, as by strapping it to a pallet, because it then remainssucceptible to being knocked down to its flattened condition andtransported for reuse.

In the illustrated container 11, the slits 45 and 47 provided in theglue flap 29 are particularly advantageous because of the over-centeraction incorporated in the closure. However, the employment of theseslits, which alleviates the tendency of the two-layer thickness ofcorrugated material to resist bending, is advantageous even if theover-center lock-action is not incorporated because it facilitates thefolding operation to form a standard bellows closure. The arrangementalso allows the glue flap to be hinged to a side panel, thus leaving thecontainer sidewalls unobstructed.

Although the invention has been illustrated with respect to a preferredembodiment, it should be understood that various modifications, otherthan those hereinbefore stated, such as would be obvious to one havingthe ordinary skill in the art, may be made without departing from thescope of the invention which is defined in the appended claims. Forexample,-if a completely die cut container blank is used, it may bedesirable to offset slightly upward the portions of the lower hinge line19b which define the inner flaps 23a and 23b. Such an offsetting isconsidered to be the full equivalent of the illustrated straight line19b, and where the term hinge line or transverse line is used in thisapplication, it should be understood to include such a partially offsetline.

Various features of the invention are set forth in the claims whichfollow.

What is claimed is:

1. A container made of corrugated fiberboard comprising fourinterconnected side panels defined by parallel fold lines and arrangedto define a tubular enclosure of rectangular cross section and fourinterconnected closure panels hinged along a line to aligned edges ofsaid side panels, a first pair of said closure panels being hinged toopposed side panels and a second opposed pair of said closure panelsbeing each divided only by a pair of converging diagonal score linesinto a trapezoidal flap and a pair of flanking triangular foldbackflaps, said first closure panels serving as first closure flaps whichare hinged to said fold-back triangular flaps, one of said first closurepanels containing a pair of first score lines oriented at an anglebetween about 82 and 89 to said hinge line, said first score linesdefining said first closure flap, and the angle between said first scorelines and the adjacent diagonal score line being less than the anglebetween said diagonal score line and said hinge line, the width of saidfirst pair of closure panels being greater than the width of said sec-0nd pair of closure panels and said length of said closure panels beingsuch that said first pair of closure flaps overlap each other in closedposition, said first closure flaps being folded inward of saidtrapezoidal flaps and said first closure flap which contains said firstscore lines being folded inward after said other first closure flapwhereby said closure becomes biased into its inward closed position uponfolding of said closure flaps.

2. A container in accordance with claim 1 wherein said first score linesare provided in both of said first closure panels.

3. A container in accordance with claim 1 wherein said diagonal scorelines are oriented at an angle of between about 46 and about 54 withsaid hinge line.

4. A container in accordance with claim 1 wherein the longitudinallength of each of said four closure flaps is equal.

5. A container in accordance with claim 1 wherein said length of saidclosure panels is between about 52 and about 60 percent of the width ofone of said second closure panels.

6. A container having four interconnected side panels arranged to definea tubular enclosure of rectangular cross section and four interconnectedclosure panels hinged along a line to the aligned edges of each of saidside panels, a first opposed pair of said closure panels forming firstclosure flaps and a second opposed pair of said closure panels beingeach divided by a pair of diagonal score lines into a central flap andtwo flanking triangular fold-back flaps, glue flap means hingedlyconnected along a vertical score line to one of said side panels and toone of said first closure panels, means adhering said glue flap with theinner surface thereof in contact with the outer surface of a side paneland of a second closure panel, first slit means in said glue flapaligned with said hinge line between said side panel and said secondclosure panel, and second slit means in said glue flap generally alignedwith the underlying diagonal score line in said second closure panelupon which said glue flap is adhered.

7. A container in accordance with claim 7 wherein said central flaps aretrapezoidal and said closure panels are of equal longitudinal length.

8. A container in accordance with claim 7 wherein said diagonal scorelines are disposed at an angle between about 46 and 54 degrees to saidhinge line and wherein said first pair of closure panels are foldedinward of said second pair of closure panels.

9. A container blank of corrugated fiberboard which blank comprises fourinterconnected side panels defined by parallel longitudinal score lines,first and second pairs of closure panels alternately connected to saidside panels along a transverse line as longitudinal extensions of saidside panels and being also defined by said parallel score lines, saidfirst closure panels being longer than said second closure panels andhaving a length between 52 and about percent of the width of one of saidsecond closure panels, a pair of first diagonal score lines in one ofsaid first pair of closure panels defining a first trapezoidal closureflap, and only a pair of second diagonal score lines in each of saidsecond closure panels which define second trapezoidal flaps andtriangular fold-back flaps which are hingedly connected to and disposedin flanking relationship with said second trapezoidal flaps, said firstand second diagonal lines meeting at an angle less than the anglebetween the second diagonal line and said transverse line, whereby saidblank is adapted for formation into a tubular container having animproved bellows-type closure when said first closure panels are foldedinteriorly of said second closure panels.

10. A blank in accordance with claim 9 wherein each of said firstclosure panels has a pair of said first diagonal score lines.

11. A blank in accordance with claim 9 wherein said parallel score linesare disposed in one surface of said blank and said first diagonal scorelinesare disposed in the surface of said blank opposite from said onesurface.

12. A blank in accordance with claim 9 wherein said first diagonal linesare disposed at an angle between about 82 and 89 with said'transverseline.

13. A blank in accordance with claim 13 wherein said second diagonallines'are disposed at an angle between about 46 and about 54 with saidtransverse line.

14. A blank in accordance with claim 9 wherein a glue flap is hingedlyconnected to one of said side panels and to one of said first closurepanels along a line parallel to said parallel score lines and whereinfirst slit means is provided in said glue flap in alignment with saidtransverse line and second slit means is provided at an angle to saidtransverse line generally the same as that at which said second diagonallines are disposed.

15. A blank in accordance with claim 9 wherein the flutes of saidcorrugated fiberboard run longitudinally thereof and wherein thelongitudinal length of each of.

said closure panels is equal.

15mm STATES PATENT armor QERTEMCATE @F CRECTEON Patent No. 790 932 DatedAugust l9 7 Inventoz-(s) Donald En It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shovm below:

Column 1, line 20, "tones" should be -tons-.

Column 3, line 4, "tapped" should be taped.

Column 5, line 53, "weighjt" should Toe weight-.

Column 7, lines 33 and 36, claim reference numeral "7", each occurrence,should read 6-.

Column 8, line 30, the claim referenoe numeral "13" should read -l2-.

Signed and sealed this 20th day of November- 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JRa RENE A D. IEGTI IEYER I Attesting Officer ActingCommissioner of Patents 'ORM PO-l 050 (10-69) US COMM'DC 60376-5 69 AQWERNMEYT PRINTING OFFICE: IBID 0-368-334,

1. A container made of corrugated fiberboard comprising fourinterconnected side panels defined by parallel fold lines and arrangedto define a tubular enclosure of rectangular cross section and fourinterconnected closure panels hinged along a line to aligned edges ofsaid side panels, a first pair of said closure panels being hinged toopposed side panels and a second opposed pair of said closure panelsbeing each divided only by a pair of converging diagonal score linesinto a trapezoidal flap and a pair of flanking triangular fold-backflaps, said first closure panels serving as first closure flaps whichare hinged to said fold-back triangular flaps, one of said first closurepanels containing a pair of first score lines oriented at an anglebetween about 82* and 89* to said hinge line, said first score linesdefining said first closure flap, and the angle between said first scorelines and the adjacent diagonal score line being less than the anglebetween said diagonal score line and said hinge line, the width of saidfirst pair of closure panels being greater than the width of said secondpair of closure panels and said length of said closure panels being suchthat said first pair of closure flaps overlap each other in closedposition, said first closure flaps being folded inward of saidtrapezoidal flaps and said first closure flap which contains said firstscore lines being folded inward after said other first closure flapwhereby said closure becomes biased into its inward closed position uponfolding of said closure flaps.
 2. A container in accordance with claim 1wherein said first score lines are provided in both of said firstclosure panels.
 3. A container in accordance with claim 1 wherein saiddiagonal score lines are oriented at an angle of between about 46* andabout 54* with said hinge line.
 4. A container in accordance with claim1 wherein the longitudinal length of each of said four closure flaps isequal.
 5. A container in accordance with claim 1 wherein said length ofsaid closure panels is between about 52 and about 60 percent of thewidth of one of said second closure panels.
 6. A container having fourinterconnected sIde panels arranged to define a tubular enclosure ofrectangular cross section and four interconnected closure panels hingedalong a line to the aligned edges of each of said side panels, a firstopposed pair of said closure panels forming first closure flaps and asecond opposed pair of said closure panels being each divided by a pairof diagonal score lines into a central flap and two flanking triangularfold-back flaps, glue flap means hingedly connected along a verticalscore line to one of said side panels and to one of said first closurepanels, means adhering said glue flap with the inner surface thereof incontact with the outer surface of a side panel and of a second closurepanel, first slit means in said glue flap aligned with said hinge linebetween said side panel and said second closure panel, and second slitmeans in said glue flap generally aligned with the underlying diagonalscore line in said second closure panel upon which said glue flap isadhered.
 7. A container in accordance with claim 7 wherein said centralflaps are trapezoidal and said closure panels are of equal longitudinallength.
 8. A container in accordance with claim 7 wherein said diagonalscore lines are disposed at an angle between about 46 and 54 degrees tosaid hinge line and wherein said first pair of closure panels are foldedinward of said second pair of closure panels.
 9. A container blank ofcorrugated fiberboard which blank comprises four interconnected sidepanels defined by parallel longitudinal score lines, first and secondpairs of closure panels alternately connected to said side panels alonga transverse line as longitudinal extensions of said side panels andbeing also defined by said parallel score lines, said first closurepanels being longer than said second closure panels and having a lengthbetween 52 and about 60 percent of the width of one of said secondclosure panels, a pair of first diagonal score lines in one of saidfirst pair of closure panels defining a first trapezoidal closure flap,and only a pair of second diagonal score lines in each of said secondclosure panels which define second trapezoidal flaps and triangularfold-back flaps which are hingedly connected to and disposed in flankingrelationship with said second trapezoidal flaps, said first and seconddiagonal lines meeting at an angle less than the angle between thesecond diagonal line and said transverse line, whereby said blank isadapted for formation into a tubular container having an improvedbellows-type closure when said first closure panels are foldedinteriorly of said second closure panels.
 10. A blank in accordance withclaim 9 wherein each of said first closure panels has a pair of saidfirst diagonal score lines.
 11. A blank in accordance with claim 9wherein said parallel score lines are disposed in one surface of saidblank and said first diagonal score lines are disposed in the surface ofsaid blank opposite from said one surface.
 12. A blank in accordancewith claim 9 wherein said first diagonal lines are disposed at an anglebetween about 82* and 89* with said transverse line.
 13. A blank inaccordance with claim 13 wherein said second diagonal lines are disposedat an angle between about 46* and about 54* with said transverse line.14. A blank in accordance with claim 9 wherein a glue flap is hingedlyconnected to one of said side panels and to one of said first closurepanels along a line parallel to said parallel score lines and whereinfirst slit means is provided in said glue flap in alignment with saidtransverse line and second slit means is provided at an angle to saidtransverse line generally the same as that at which said second diagonallines are disposed.
 15. A blank in accordance with claim 9 wherein theflutes of said corrugated fiberboard run longitudinally thereof andwherein the longitudinal length of each of said closure panels is equal.